This Partaker mini PC runs pfSense out of the box but is also compatible with Windows 10 and most Linux distributions. Powered by the 15W i3-8130U the compact 178 x 126 x 55mm system features M.2, 2.5" storage options, four USB 3.0 ports, HDMI, and a spectacular array of six Intel LAN. It's available for $422.99 but a more affordable Celeron is also available from $245.99.
